New Perspectives on XML

1

• Tutorial 1.1
• History and Theory of XML

2
Introducing XML

• XML stands for Extensible Markup Language. A
  markup language specifies the structure and
  content of a document.
• Because it is extensible, XML can be used to
  create a wide variety of document types.

3
Introducing XML

• XML is a subset of the Standard Generalized
  Markup Language (SGML) which was introduced in
  the 1980s. SGML is very complex and can be
  costly. These reasons led to the creation of
  Hypertext Markup Language (HTML), a more easily
  used markup language. XML can be seen as sitting
  between SGML and HTML easier to learn than
  SGML, but more robust than HTML.

4
The Limits of HTML

• HTML was designed for formatting text on a Web
  page. It was not designed for dealing with the
  content of a Web page. Additional features have
  been added to HTML, but they do not solve data
  description or cataloging issues in an HTML
  document.
• Because HTML is not extensible, it cannot be
  modified to meet specific needs. Browser
  developers have added features making HTML more
  robust, but this has resulted in a confusing mix
  of different HTML standards.

5
Introducing XML

• HTML cannot be applied consistently. Different
  browsers require different standards making the
  final document appear differently on one browser
  compared with another.

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The 10 Primary XML Design Goals

1. XML must be easily usable over the Internet
2. XML must support a wide variety of applications
3. XML must be compatible with SGML
4. It must be easy to write programs that process
   XML documents
5. The number of optional features in XML must be
   kept small

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The 10 Primary XML Design Goals Continued

1. XML documents should be clear and easily
   understood
2. The XML design should be prepared quickly
3. The design of XML must be exact and concise
4. XML documents must be easy to create
5. Keeping an XML document size small is of minimal
   importance

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XML Editors
This figure shows available XML editors
9
XML Parsers

• An XML processor (also called XML parser)
  evaluates the document to make sure it conforms
  to all XML specifications for structure and
  syntax.
• There are two categories of XML documents
• Well-formed
• Valid

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XML Parsers

• Microsofts parser is called MSXML and is built
  into for IE versions 5.0 and above.
• Netscape developed its own parser, called
  Mozilla, which is built into version 6.0 and
  above.

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Well-Formed and Valid XML Documents

• An XML document is well-formed if it contains no
  syntax errors and fulfills all of the
  specifications for XML code as defined by the
  W3C.
• An XML document is valid if it is well-formed and
  also satisfies the rules laid out in the DTD or
  schema attached to the document.

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The Document Creation Process
This figure shows the document creation process
13
Working with XML Applications

• XML has the ability to create markup languages,
  called XML applications. Many have been developed
  to work with specific types of documents.
• Each application uses a defined set of tag names
  called a vocabulary. This makes it easier to
  exchange information between different
  organizations and computer applications.

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XML Applications
This figure shows some XML applications